In reply to MeMeMe:
A few hints I've come across and a few things I've done myself.
1) rinsing the tent in a 50/50 water and vinegar solution and air drying in the shade can stop a PU coating from being sticky.
2) Alternatively remove the old PU coating (give it a wash or hand wash and let it soak) once with dish soap and then with nomal powder, scrub off the old Pu coating, give ot a rinse and let it dry and then apply "McNett’s Gear Aid Tent Sure Polyurethane Sealant". If this isn't availiable I think you can dilute seam grip at about 30:1 with Toulene, though I haven't tried.
3) Once done Use Fabsil Gold on the outer, avoid getting the seams coated as it will absorb through the stitching and cause the seam tape to degrade faster.
4) If the seams need resealing, use seam grip diluted with Toulene (3 parts Toulene to 1 part glue I think, though don't quote me).
Best of luck
Post edited at 06:54